Inlet valve for gas compressors



Nov. 5, 1946. w. s. POWELL 2,410,522

, l INLET VALVE FOR lGAS COMPRESSORS w Filed June 17, 1942 BY'Y @vanaf-M Patented Nov. 5, 1946 ZAlZZ rNLE'r VALVE Foe Gas oor/.transenne 9 I William" S. Powell, Indianapolis, Ind., assignor to Marmon-Herrington Company, inc.,A Indianapolis, ind., a corporation of-Indiana.

Application J une 17, 1942, Serial No. 447,47!

`In the operation of modern airplanes,r maintenance of a supply of compressed air is an essential, While, at the same time, conservation oi power requisite for such maintenance is desirable.

Heretofore, it has been customary t'o` provide a compressor and a motor, generally electric, so proportioned that the motor is capable of aotuating the compressor at full capacity at ground level to deliver compressed air to the desired maximum pressure and in such an arrangement, at higher levels due to the lower pressureoic air supply, the maximum power of the motor is much greater than is required.

rEhe object ofVY my invention is to provide an` improved method and means by'whiohthe quantity of air which may be-supplied-toa compressor on its suction stroke, at its normal rate of speed, will be varied inaccordance with the barometric pressure of the air supply and, as av supplement, inaccordance with the temperature of the air supply, so that the massgof compressed air discharged at each stroke (unit operation) of the compressor will be substantially uniform irrespec tive of the altitude of the apparatus and ternperature of the air supply.

The accompanying drawing illustrates my invention.

Fig. v1 is a diagrammatic illustration of` an embodiment ofV my invention;

Fig. 2' an axial section of an appropriate coinv presser inlet valve and associate barometricallysensitive controller; I

Fig. 3Y an axial section of another trolled inlet valve; v

Figwi a fragmentary section showing athermally-responsive "addition to the structure' of Fig. 2;

Fig. 5a sectionronv an enlarged scale, of an.

appropriate needle -valve and associate seat; and Fig. 6 a section, on a smaller scale, of a niotiii F1-ed form. y v

ln the drawing, laindicates'an air-compressor or any desired form' driven by a motor I`I and provided with a discharge duct I2 leading to ay storage chamber I3; and an inlet duct I4 openA to atmosphere. 1

rllhe motor i I need only'be powerful enough to eiectively drive vthe compressor at thev highest f contemplated altitude and, therefore, much too small to effectively drivethe compressor atfull capacity when at ground 1evel., Therefore, in order to render such amotor effective at ground level,I part of the inlet'du'ct lffl'comprisesa-valve seat I5 and cooperating valve- It;- thefpositionfci which relative to seat- I5-is subiectftother-control formof con# y 3 Claims. (Cl. 230-2) of av barome'trically sensitive cell l l in" such man-` ner thatth'epas'sage between seatl land" valve it will varyf'inversely' with variations of baro metric" pressure so that the successive masses of air which may enter the compressor during suc-v cessve-suction strokes, atrnormalspe'ed-of operatioifio'f'th'eicompressor, willi be uniform,.i. e., lessi volume-of admitted air at atmospheric pressureat 16W altitudes thanv at high( altitudes.

As the mass of air in a" given volume varies inversely withits temperature, it may also be desirable' to control the position of valve Iliin accordan'ce with variations init'einper'atur of theV air supply', valve i6 being' near'erto` its seat,` at'.

a given barometricl prssur'e,.when the air supply isV cold' than when" the" airis at a higherte'mperature.

For that purpose, cell if'lmay be supported upon a thermally responsive support so that itseiectv valve of the needle type, as shown in Fig. 5, wiltl be' most convenient, though I wishY itrunderstood thatjmy invention is not limitedto suchY form.

The proper' contour of valve I'vmay be readily determined mathematically' so that for all posi'- tions-of the valve relative to` its seat under current conditionsof supplyV pressure (and tempera'fture if desired) itr will permit only a flow ofa` predetermined, mass of air' per unit of time into;A

the compressor.

Uniform.massesof` airmaybe compressed to a. predetermined pressureby the expenditure...ci` Consequently, the. motor.H il at low altitudes'will becalled uponfor the same amount of work as at higher altitudes' uniformv quantities. of power.

prises a circumferential flange 2li which may'seatv on the annular seat I5, and a tapered plug'po'rtion 2| the various diameters of which are so proportioned as tofvariably block theeye of seat I5 as the valve is axially shi-ftedinaccordance with altitude variations.

Valve seat I5 is anchored in bore 22 of nipple 23 and valve I6 is biased toward seat I5 by a spring 24.

21, 21, sealed together, mouth to mouth, at their perimeters and axially slidable' in a foraminous shell 28 which, at its perimeter,- is formed to fit cup 25 and, at the same time, aiord air passages to valve seat l5, as indicated by arrows. Shell 28 is held in place by a retainer ring 28'.

One cup 21 of the barometric cell, at its center,

n is anchored to shell 28 while the other cup 21,

at its center, is provided with a pocket 29 into which the adjacent end of valve i6 seats As thepressure of the air surrounding cell Il decreases, the cell bulges at its center and this so positions valve I6 relative to its seat I5 in accordance withY the altitude of the device that uniform masses of air Vare admitted vto the` compressor at what-v ever maybe the altitude of the apparatus.

The proper contour of valve IB, taking account only of barometric pressures, may be determined t as follows: 1

If the total amount of movement of valve IE is designated by the letter M thenthe requisite movement of the valve for proper altitude position will be proportionate parts of M as shown in Fig. 5 and outlined below. t

If the diameter of the total opening is designated by the letter D then the diameter of the valve at various altitudes must be made to match the amount of motion of the plunger and regulate the air inthe proper amount.

Actual values of D and M vary with the capacity of any device upon which the valve is used. The properrelationship, when the compressor operates to attain a maximum pressure of 1000 pounds, may be determined in the following manner:

. Valve Diameter of Altitude (feet) motion valve at M t (M) (alt.)

The variables involved in the calculations can all be simplied by utilizing the weight of the air to behandled rather than thevolume, because themass varies continually with the altitude and the temperature.

1 cubic foot of air at 40,000 ft. weighs 4 Note: Comparative areas:

A 1/8 in. dia. hole has an area .0122 in.2

.000576: .00057 6X 19.5: .01122: .53x28 1.485 1.485 Tes-o A 35" dia. hole has an area .0069 in.2

.00756 sq. in.=area of the orifice to pass .000576 lb. of air/sec.

Y Check:

It the pressure is 14.7 lb. 1 in.2 and the temperature is 0, one ft.3 of air will weigh .08635 lb.

`An opening .00756 in.2 will pass .00756 sq. in.

.003742 lb. of air per sec. (6l/2 times too much). Therefore the opening will have to close to- .000575 E m -00756=1538=-00116 111.2 at 125 F.

An opening .00116 in.2 willpass .000615-'X1507 :.000374 lb. ofl air/sec. at 125 F.

3": rounding air serving to lengthen or shorten the connection between cell I1 and valve i6.

Cup 25 may be provided at its mouth with screens 3l and filter 32 held in place by ring 33.

Referring to Fig. 3, 40 indicates the main body of an inlet valve structure having an entry passage 4| provided with a valve seat 42. Cooperating with seat 42 is a. valve 43 anchored on one wall 44 of a barometrically sensitive cell I1', the opposite wall of which is provided with ears 45 pivoted at 46 to one end of a stem 41 projected through an arch 48'of body 4l] between nuts 49 and 50.

Leading into passage 4l, on the discharge side Y, of Valve 43, is an inlet passage 52 controlled by a In order to compensate for temperature variations, a 'ni-metallic temperature responsive cushion 30 (Fig. 4) may be interposed between valve l0 and pocket 29, expansion or contraction of this cushion by reason of temperature of the surneedle-valve 53.

In use, stem 4l' may be so adjusted that, at ground level, valve 43 is spaced from seat 42 to aiord entry of the'proper mass of air to permit motor H to function.

As the altitude of the structure rises, cell l'l will bulge so as to move valve 43 away from seat 42 to admit additional volumes of air, at lower pressure due to altitude, so that the air flow through the structure in a unit of time, will be a predetermined mass within the capacity of the compressor motor.

It will be noted that with the described arrangement, the masses of air which may enter the N compressor for successive charges will be uniform irrespective of variations of atmospheric pressure. Therefore, this desired mass having been determined, an energizing motor for the compressor'may' beselected which, at its delivery speed; will operate at its highest efciency at all times. Such an arrangement therefore reduces to a minimum, weight and size of the unit.

In order to minimize temperature effects, a construction'like that shown in Fig. 6 may be used. In this form an evacuated sylfon cell 21' has suicient expansive axial resilience, when external pressure is reduced, to move valve 2| from its seat. This cell is sup-ported in the main body 25 by the foraminous shell 282, as in the construction shown in Fig. 2. Because of the reduced air content of cell 21 variations of temperature of the surroundings of the cell have little eiect on the pressure Within the cell.

I claim as my invention:

1. An inlet valve structure for air compressors, comprising a pair of elements relatively shiftable to control passage of air therebetween and a barometrically-sensitive unit associated with said elements so as to control their relative position in accordance with the pressure of air admissible between said two elements, and including a thermany-responsive element interposed between the barometrically-sensitive unit and one of said pairs of elements.

2. An inlet valve structure for air compressors, comprising a pair of elements relatively shiftable to control passage of air therebetween and a barometrically-sensitive, evacuated, inherently expansive cell associated with said elements so as to control their relative position in accordance with the pressure of air admissible between said two elements, and including a thermally-responsive element interposed between said cell and one of said pair of elements.

3. The combination with an air 4compressor and an actuator of insuflicient power to drive the same at full capacity at ground level, of a valve controlling the inlet of said compressor, and a barometrically-sensitive, evacuated, and inherently expansive cell within the influence of the air supply for said compressor and connected to said inlet valve to control its effective position relative to the compressor inlet, whereby substantially uniform masses of air will be drawn into the compressor upon unit operation of said compressor irrespective of the pressure of air supply due to altitude of the compressor.

. WILLIAM S. POWELL. 

